Capacitors may be used with or in many different types of integrated circuits or microchips (“chips”). For example, metal-oxide-semiconductor (“MOS”) capacitors may be formed on a substrate, and may be used in circuits including, for example, filters, phase-locked loops, memory circuits, voltage control oscillators, switching circuits, or amplifiers. Additionally, such capacitors may be formed off of a chip containing the rest of the circuit(s), and then connected to the chip for operation of the circuit(s) as a whole.
A given example of such circuits may be implemented as either a single-ended circuit or as a differential circuit. For example, a differential circuit may be implemented as two single-ended circuits, where the two single-ended circuits are provided with different power supply and/or ground references with respect to one another. Then, for example, by designing and/or operating the references and/or the differential circuit such that signals input to each of the included single-ended circuits are equal and opposite of one another, various benefits may be obtained. For example, common-mode noise that is input to both of the two single-ended circuits may be rejected, and even-order distortions in the circuit(s) may be canceled at the differential output.
An example of a circuit that may be single-ended or differential includes a differential filter. In many differential filters, inputs to single-ended and/or differential circuits thereof, may have a varying range of operating characteristics, such as, for example, varying frequencies, voltages, temperatures, or other characteristics. For example, circuit components involved in producing the inputs may produce outputs that vary in one or more of the above-described characteristics (or in other characteristic(s)). In one specific example, a transistor connected to an input(s) of a differential filter may have a frequency that varies over time.